38 SOME SOUTH INDIAN INSECTS, ETC. [CHAP. IV. 



Both these forms of mimicry are founded on the fact that the 

 normal enemies (especially birds, lizards, and amphibians) learn 

 by actual experience which of their insect-prey are palatable or the 



reverse. A young bird, which first commences to forage for itself 

 and catches (let us say) a white moth or a yellow-and-black wasp 

 and finds that it has a nauseous mouthful or that it has been badly 

 stung, will quickly learn to avoid insects which are pure-white or 

 black-and-yellow in colour. Armchair critics may deny this, but 

 no one who has lived for any time in the tropics and experimented 

 on the gastronomic educability of insectivorous animals is likely 

 to agree with them, and we may safely affirm that insectivorous 

 animals do leain by experience to avoid insects of certain (generally 

 conspicuous) types of coloration. Such common types are bold 

 mixtures of red and black, black and yellow, red and white, white and 

 (less commonly) other mixtures, of blue and yellow, etc. Generally 

 speaking, we may say that an insect which is conspicuous in its 

 normal environment is nauseous in taste and that such insects fall 

 into a very small number of types of " warning " coloration. 



The result of this state of things is of equal benefit to the insec- 

 tivorous animal and the nauseous insect, the former having only to 

 learn a few common colour-combinations in order to know which to 

 avoid as food, the latter having only to sacrifice a small proportion 

 of its individual numbers in order to secure immunity after a shoii 

 period of sampling on the part of each individual enemy. For 

 example, if all wasps were coloured differently (some red and black, 

 some white and black, some green, some yellow, some green 

 and yellow, some blue and yellow, etc.), every insectivorous bird 

 would have to sample at least one individual of each differently 

 coloured kind of wasp and would have to remember which forms 

 were palatable and which were not; whilst actually, most wasps 

 being coloured black and yellow, a very tew tests on individuals so 

 coloured teaches the bird to avoid insects exhibiting those colours, 

 with equal benefit to the bird and the insects, as the former incurs 

 fewer unpleasant experiences and the latter avoid considerable loss 

 in individuals, collectively at least. For it must be remembered, as 

 a general rule, that an insect attacked usually connotes an insert 

 destroyed ; an unpalatable insect may be rejected after capture, hut 

 often it is then in such an injured condition as to be practically 

 moribund. 



From this it will be seen that tin- individuals of species forming 

 a Mullerian mimetic group are practically members of a mutual- 

 benefit association. If one individual each of species A and B 

 suffice to teach a young bird that their common type of coloration 

 is of a " warning " character, then other individuals of species, 



